frequency of wave is defined as ratio of speed and wavelength
here we know that for ultraviolet light speed is given as
[tex]c = 3 * 10^8 m/s[/tex]
also the wavelength is given as
[tex]\lambda = 150 nm = 150 * 10^{-9} m[/tex]
now we know that
[/tex] f = \frac{c}{\lambda}[\tex]
[tex]f = \frac{3*10^8}{150 * 10^{-9}}[/tex]
[tex]f = 2 * 10^{15} Hz[/tex]
so here frequency of light is 2 * 10^15 Hz